Patent GB-694722-A (GB)
Title: Improvements in or relating to devices for shifting spring systems
IPC: F16D25/08
Filed: 1950-03-07
Abstract: 694,722. Controlling friction clutches. AKTIEBOLAGET LJUNGSTROMS ANGTURBIN: March 7, 1950 [March 7, 1949], No. 5735/50. Class 80 (ii). [Also in Group XXXII] A spring loaded system comprises a shift member, for controlling the spring load applied to elements of the system, and an actuating mechanism for shifting said member, consisting of an axially fixed member, a control member having limited turning movement between two terminal positions, and cam means providing operative engagement between the control member and the fixed member and operative to cause axial movement of the control member in predetermined relation to its turning movement when the control member is turned, the cam means disengaging the control member to leave it free from the fixed member in the terminal position, means being provided to give an axially fixed connection between the control member and the shift member. As shown, a double-acting clutch 14 of the over-centre type connects a motor-shaft 20 either to a hydraulic torque converter 12 or direct to a driven shaft 47. The clutch 14 is embodied in a flywheel 50 having the form of a double plate 50a, 50b between which is disposed a pair of friction discs 52, 54. An actuating plate 56 is axially displaceable in the space between the two friction discs, the actuating force being produced by a belleville washer 58 clamped to it and pivotable between ribs 60, 62. At its inner circumference, the belleville washer is axially displaceable by a shifting mechanism 66, the washer projecting into a peripheral groove in a hub ring 67. According to which friction disc 52, 54 engages with the flywheel 50, the motor shaft 20 drives either the driven shaft through disc 52, in which case the hydraulic converter is bypassed, or the pump shaft 24 of the hydraulic converter through disc 54. A pin 68 is fixed to the hub-ring 67 and engages a radially extending slot in the belleville washer 58, which rotates with the actuating plate 56 on a bearing 70 between the ring 67 and a sleeve 72. In a modification, not shown, the belleville washer 58 is replaced by a number of helical springs on Lever arms which produce the actuating force. In a further modification, not shown, a clutch of the single acting type has the outer periphery of a belleville washer attached to the flywheel, axially moving helical springs urging an actuating plate away from the clutch friction disc on shifting from engaged to disengaged position, To produce the axial displacement of the inner circumference of the hub-ring 67, belleville washer 58 and actuating plate 56 necessary to engage and disengage the clutch, the sleeve 72 is provided with peripheral cam grooves 74 of varying axial location in which move pins 80, surrounded by rollers 78, on an operating ring 76. The operating ring 76 is thereby displaced axially on being rotated, in accordance with the shape of the grooves 74, and this movement is transmitted to the hubring 67 through the bearing 70. The axial limits of the groove are such that the inner edge of the belleville washer may be displaced from one outer position to the other, corresponding to the engagement of the two clutch discs 52, 54; these two outer positions are situated on either side of a neutral position when the belle-ville washer is in unstable equilibrium. The shape of the grooves 74, Fig. 10, is so chosen that the turning force, required to rotate the operating ring 76 is substantially constant, although the axial force required to move the belleville washer 58 varies. The ends of the grooves 74 are widened so that the roller 78 is not in contact with it in the two end positions a<SP>0</SP> or a<SP>5</SP>, the clutch discs 52 or 54 then being engaged so that eccentricity, if any, between the rotating clutch parts and the sleeve 72 does not influence the operating ring 76. When neither of the clutch discs .52, 54 is engaged, the belleville washer 58 is in unstable equilibrium at its central or neutral position, and the two projections 84, 86 in the walls of the groove 74 provide a dwell-point in which the roller 78 is retained. In a modification, not shown, the positions of the grooves 74 and rollers 78 are interchanged, so that the grooves are in the operating ring 76, and the. pins 80 and rollers 78 are mounted on the sleeve 72. The operating ring 76 is turned by means of a forked arm 77, Fig. 5, the end 90 of which is actuated by a servo-motor 88 operated by pressure oil supplied through a two-part control slide 94a, 94b. The slide 94a, 94b alters the state of a selector-valve by which the piston 96 of the servo-motor is moved into one of three positions, at either end of its cylinder and in the middle thereof, corresponding to the two ends of the groove 74 and its dwell-point. The operating means provided for the modified form of single-acting clutch which the specification also described are similar, but the grooves 74 then have no central dwell-point, and the servo-motor has two working positions only, one at each end of its cylinder.